A trajectory of Zostera marina (eelgrass) ecosystem recovery: pre- and post-Hurricane Sandy degradation in Barnegat Bay, New Jersey

Abstract

In 2012, Hurricane Sandy struck Barnegat Bay, New Jersey damaging extensive beds of Zostera marina and causing major benthic ecosystem disruptions. Pre-Sandy genetic surveys of eelgrass populations in Barnegat Bay indicated low heterozygosity and connectivity with high levels of inbreeding. After such devastation, we became concerned with the long-term fate of these populations and in previous work examined the present genetic condition of eelgrass in Barnegat Bay. Counter to our expectations, the 2021 Z. marina populations were more diverse, had greater connectivity and less inbreeding than the populations from 2008. These results further motivated us to examine the trajectory of changes between 2008 and 2021 through additional investigation of archival Z. marina samples from 2013 and 2017. This present study tracks the trajectory of Barnegat Bay eelgrass population genetics before and after Hurricane Sandy. Immediately post Sandy, populations were already more diverse with heterozygosity closer to Hardy-Weinberg Equilibrium; by 2021, two populations, Oyster Creek and Ham Island, demonstrated a surplus of heterozygotes. Similarly, in 2013 there was a three to eight-fold reduction in inbreeding observed with clear outbreeding by 2017. There was no evidence of recent bottlenecks in any population, although Oyster Creek and Ham Island populations manifested historical bottlenecks. Our evidence supports that genetic recovery was already underway a year after Sandy.